Low Scaling Quantum Chemistry (LSQC) Program

Table of Contents

  1. Introduction

  2. Documentation and License

  3. Modules

  4. References

  5. Contacts

Introduction

Low Scaling Quantum Chemistry (LSQC) program (No. 2006SR09617) is a quantum chemistry package for linear or low scaling electronic structure calculations of large systems, which was developed by the research group of Professor Shuhua Li and Professor Wei Li in Nanjing University. The original version is LSQC-1.0 published on April 20, 2006, and the current version is LSQC-2.5 published on Jan. 20th, 2022. This version supports serial and Intel MPI parallel calculations, and can be run on most Linux systems.Current LSQC program supports two methods for electronic structure calculations of large systems. The first one is the generalized energy-Based fragmentation (GEBF) method and the other one is the cluster-in-molecule (CIM) local correlation method. The latest information of LSQC program can be found via our website at http://itcc.nju.edu.cn/lsqc or the following QR code:

Documentation and License

Modules

GEBF

Within the GEBF approach, the total energy of a macromolecule can be directly obtained from the energies of a series of subsystems, which can be obtained from running conventional quantum chemistry calculations. The approach can lead to good results for close-shell systems with localized electrons, such as biomolecules and polymers. For systems with hundreds and even thousands of atoms, the GEBF-X approach allows full quantum mechanical (QM) calculations at the X level to be accessible on ordinary workstations.

The calculations of electrostatically embedded subsystems at various theoretical levels can be done with existing quantum chemistry programs. In this version, only Gaussian program is supported for subsystem calculations.

The single point calculation (SP) at semi-empirical method (AM1, PM3, PM6, etc), HF, DFT and electronic correlation method (MP2, MP3, MP4, CCSD, CCSD(T)) is available in current version. And the geometry optimization (Opt), frequency (Freq), IR intensity, Raman intensity, zero-point energy, enthalpy, Gibbs free energy, dipole moment, static polarizability, hyperpolarizability and NMR are also available in this version.

PBC-GEBF

Within the PBC-GEBF approach, the ground-state energy per unit cell for molecular crystals or liquids of small molecules can be readily available at various theoretical levels. For these systems, a molecule is automatically taken as a fragment (by default). Specially, one can obtain PBC-GEBF-X (X=MP2, CCSD, DFT, HF, …) energies for periodic systems mentioned above.

CIM

Within the CIM approach, electronic correlation equations are solved within the representation of occupied and virtual localized molecular orbitals. For a target molecule, the clusters are built from localized molecular orbitals automatically by the program. The approximate correlation energy of the target molecule is obtained from the correlation energy contributions of a series of clusters, which are solved independently. Single point energy at CIM-MP2 and CIM-RI-MP2 levels is available in current version. In addition, conventional MP2 and RI-MP2 calculations for medium-sized systems are also supported.

Database

References

Publications using GEBF module should cite the following references:

Publications using PBC-GEBF module should cite the following references:

Publications using CIM module should cite the following references:

The license of Gaussian should be available for you and cited if Gaussian program is employed for subsystems calculations. See http://www.gaussian.com/ for more information.

In the CIM calculations, the Hartree-Fock calculations are performed by the PySCF package and the electron integrals are obtained by Libcint electron integral library. The corresponding references should be cited. See https://pyscf.org/ and https://github.com/sunqm/libcint for more information.

Contacts

LSQC Group: